ENDGAME BUILD. NEW Souls-like game, Remnant: From the Ashes. Trait level 198 (required traits - 80, for the build). Build is focused on BLEED dmg, BOSS burn, and ONE shots. Boss shown is Claviger. Roll + proc 00:55. Normal melee crit impact on boss 00:59. Bleed dmg 01:02. Second normal melee crit impact 01:44. Character screen 01:59. (link to build: https://imgur.com/a/dD7W2Dz)

UPDATE(1): Boss kills. Undying King in 38 seconds, Hard +20 - https://youtu.be/uHFA8xiFt14
UPDATE(2): Razorstone ring changed from 200% to 100% as of 8/20/19. BUILD UNCHANGED. Multiplier is (normal crit) x 8 instead of (normal crit) x12. Was a bug originally, at 200%.
UPDATE (3): AKARI SET NERFED, as of 8/20/19, down to 5 second buff (from 10 seconds). This is unfortunate, because it was nice having that much breathing room to run up and prep the big hit. HOWEVER, the build is still functioning. The big damage is still there - will just need to time an additional roll (every 5 seconds). I will continue to run tests.
UPDATE (4): After the Akari set NERF (undocumented change), it is much harder to pull off the melee chains on bosses. The damage is STILL there, however there are very few bosses that can actually attack you to instigate the buff. The adds would originally allow you enough time to roll dodge, then run over to the boss to DPS. This is much harder now (it is possible - with higher risk - mobs will need to be near boss swinging, or boss attacking you).
UPDATE (5): Will continue testing, but the build still works. A few bosses are more challenging now with timing the rolls against the adds. Clearing to the boss still functions the same.
Post-nerf boss fight(s): Shroud on nightmare +20 https://youtu.be/zc7eDWPpP28
**Will continue to test the boss fights post-nerf, but it appears the build is still viable. The strategy now is to melee as much as possible with only Hunter's mark up. If you can dodge, then prioritize that, otherwise normal melee is sufficient damage.
UPDATE (6): New patch notes for 8/22/19 saw two more nerfs, but they are smaller than the previous patch. Reduced Catalyst buff (20% to 15%), Increased Hunter's Mark buildup (750 to 1000) . This will bring the proc chance for the big crit down to 20% (from 25%). And hunter's mark will take slightly longer to activate. Rest of build OK.
UPDATE (7): Devs are looking into Akari set, at 5 seconds being too low. GOOD NEWS. 8/23/19. Will keep this updated if anymore changes come in. THE DEVS ROCK.
UPDATE (8): SEE POST FOR UPDATES (AKARI SET BUFFED 8/29/19) https://www.reddit.com/r/remnantgame/comments/csjmjn/crazy_melee_build_big_hits/

My gear is +20, and the game is set to HARD difficulty. Total kill time for boss was 1 min 30 sec. This time can be further improved . The BIGCRI
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https://www.youtube.com/watch?v=f2xfDKcOwhE